Pedicle flaps of skin and subcutaneous tissue are essential to the successful functional and aesthetic reconstruction of defects of congenital, traumatic, and malignant origins. Free flaps may offer a more versatile means for achieving this goal. The aim of this proposal is to study and compare the metabolic alterations occurring in association with construction and utilization of cutaneous pedicle flaps and free flaps. The surgical procedure of "delaying" the skin flaps before transfer to a new position improve flap survival. We propose the mechanism of delay phenomenon to be a metabolic adaptation of flap tissue to the altered cellular environment. The hypothesized adaptation is one which we have found commonly in healing systems previously studied. This proposal includes the study of intermediate steps of energy metabolism and the study of overall rates of carbohydrate, amino acid, and nucleic acid metabolism. Cyclic nucleotide metabolism will be investigated to elucidate the beneficial effects of adrenergic receptor blockers on flap survival. The microanalytical techniques are essential to the metabolic investigation of various skin structures such as the epidermis, hair follicles, dermis, subcutaneous muscle, and blood vessels. Vascular changes secondary to the delay will be documented by investigating the blood flow (utilizing radioactively tagged microspheres) and nutrient microcirculation (by means of the 2-deoxy-(14C) glucose method) and will be correlated with the data on metabolic adaptations in flap survival.